Seat suspension arrangement and adjustment mechanism therefore

ABSTRACT

A seat arrangement comprises a platform element in the form of a wire grid comprising side rails (1) between which extend a plurality of supporting wires (3) having angled portions (3A) such that the platform element is transversely extensible under load. The side rails (1) are linked to a seat frame (5) by wire links (6) that are subject to a seat frame that are subject to only limited extension so that the rails are (1) are held thereby against substantial displacement from the plane of the frame (5). The rails (1) are also linked to the frame (5) by way of Bowden cables (9) that are anchored to the frame forwardly of the side rails (1) and that can be contracted to draw portions of the side rails (1) forwards between adjacent wire links (6), thus varying the contour of the platform element to provide adjustable lumbar support.

This invention concerns an improved seat suspension arrangement of thekind enabling the contour of the support provided by a seat to beadjusted by the user. The arrangement is particularly intended for usein the backrest of a vehicle seat of the kind providing adjustablelumbar support, but it will be appreciated that the principle may beapplied to any other arrangement wherein the contour of a seat cushionis desired to be adjusted, for example to a seat base having means forproviding adjustable thigh support.

A seat arrangement in accordance with the invention comprises a seatframe and a platform element adapted to provide support for upholsteryof the seat, the platform element being linked to the seat frame by linkmeans extending between the frame and at least one margin of theplatform element, the said platform element being so constructed that itis resiliently extensible in a direction towards said margin of saidseat frame, means being provided for adjusting the effective length ofsaid link means, the arrangement being such that with the link means inan extended condition at least one portion of the platform element isrecessed relatively to a boundary of the seat frame forming anattachment for the link means, and said adjustable link means beingsupplemented by further non-adjustable link means for retaining theposition of the margin of said platform element relatively to the seatframe whereby upon contraction of the adjustable link means said portionof the platform element is displaced towards said boundary in order tovary the contour of the said platform element.

Further preferred features and advantages of the invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings and any appended claims.

The invention is illustrated by way of example in the accompanyingdrawings, in which;

FIG. 1 is a front view of a suspension platform for a seat back of avehicle, shown in place in a vehicle seat frame indicateddiagramatically, together with an associated adjusting arrangement,

FIG. 1A is a detailed plan view of a link 6 of FIG. 1.

FIG. 2 is a sectional plan view taken on the line II--II of FIG. 1,showing the platform element in one stage of adjustment,

FIG. 3 is a view similar to that of FIG. 2 showing the platform elementin another state of adjustment,

FIG. 4 is a sectional view on the line IV--IV of FIG. 1 showing theinternal arrangement of the adjustment mechanism in the position shownin FIG. 2,

FIG. 5 is a view similar to that of FIG. 4 but showing the adjustmentmechanism in the position corresponding to that of FIG. 3 of thedrawings,

FIG. 6 is an exploded view showing individual components of theadjusting mechanism of FIGS. 4 and 5, and

FIGS. 7A-7C, 8A-8C, 9A-9B, and 10-11 are detailed views of individualcomponents of the assembly shown in FIG. 6.

Referring to FIG. 1, a platform element for supporting the upholstery ofa vehicle seat back comprises a pair of side rails 1 formed in knownmanner of paper wrapped or plastic coated steel wire, the side railsbeing angled at their lower ends and interconnected by means of a clip 2to form a U-shaped outer boundary of the platform element.

Between the side rails 1 are provided a plurality of transversesupporting wires 3 that are angled at 3A so that they form sinuous wiresprings allowing for limited transverse stretching of the platformelement. The longitudinal pitch of the transverse supporting wires 3 isvaried in accordance with the desired support to be provided by theplatform element, in generally known manner, and the transversesupporting wires 3 are interconnected at their mid points by means of acentral longitudinal cord 4 penetrated by the wires 3.

A seat frame is indicated diagramatically at 5 and the platform elementis suspended in the seat frame by means of wire links 6 tensionedbetween the side rails 1 and the seat frame 5. The wire links 6 are alsoangled to allow limited resilient extension thereof, as shown in FIG. 1Awhich is a detailed plan view of a link 6 of FIG. 1.

The transverse supporting wires 3 are anchored to the side rails 1 bybeing wound around the latter in such a manner that they compress thepacer or plastic covering of the side rails and and are thereby retainedin their longitudinal spacing. Such an arrangement will be well known toone skilled in the art.

In the region of the platform element that is intended to provide lumbarsupport for the occupant of the seat, there are attached to the siderails 1 sheet metal brackets 7 that engage around the side rails 1 andalso provide an anchorage for the outer sheaths 8 of a pair of Bowdencables coupled to a manually actuatable adjusting mechanism indicatedgenerally at 10 and to be described in more detail below.

The Bowden cables 9 extend from the outer sheaths 8 and pass through thebrackets 7, the ends of the cables being linked to the seat frame 5 byanchor portions 11.

The seat frame 5 is of channel section as shown more clearly in FIG. 2,and, whereas the links 6 extend in the plane of the platform element andare coupled to tabs 5A at the rear of the frame 5, the anchor portions11 are coupled to the front of the frame 5 so that, when the adjustingmechanism 10 is in one end position of adjustment, the position of theplatform element relatively to the seat frame, in the region that islinked to the Bowden cables 9, is substantially as shown in FIG. 2, inwhich the support provided by the platform element extends in aconfiguration that is generally concave relatively to the margins of theseat frame 5.

In this position, the portions of the Bowden cables 9 extending betweenthe seat frame 5 and the brackets 7 act effectively as wire linksdetermining the positions of the adjacent portions of the side rails 1relatively to the seat frame 5. Thus, by actuating the adjustmentmechanism 10, for example by means of a manually actuatable leverconnected to the end of rotary shaft 10A, the Bowden cables can beretracted relatively to the brackets 7, thus shortening the linkscoupling the side rails 1 to the frame 5 at this point.

As a result, the platform element can be tensioned forwardly until theportions of the side rails 1 adjacent the brackets 7 adopt a positionrelatively to the frame 5 that is shown in FIG. 3. It will beappreciated that since the wire links 6 are subject only to limitedextension, in comparison for example to coil springs, tensioning of theBowden cables caused change in the contour of the platform elementrather than displacement thereof as a whole.

Thus, the degree of lumbar support provided by the platform element canbe increased by actuation of the mechanism 10.

This arrangement has the considerable advantage in comparison with knownmeans for providing adjustable lumbar support, that the overall positionof the platform element is not displaced relatively to the seat frame.In known arrangments, wherein the profile of the platform element isvaried to provide lumbar adjustment, the disadvantage can arise thatwhen the platform element is angled to increase lumbar support thesuspension means yield to allow the platform element to move rearwardlythus reducing the effectiveness of the lumbar adjustment.

FIGS. 2 and 3 show the two extreme positions of the lumbar adjustmentprovided in the embodiment described, and it will be appreciated that incontracting the Bowden cables 9 in order to achieve movement of theadjacent portions of the side rails 1 from the position of FIG. 2 to theposition of FIG. 3, the tension in the Bowden cables progressivelyincreases, so that the force that must be exerted by the adjustingmechanism varies accordingly. This effect has also been found to occurin other forms of seat adjustment that have hitherto been effected bymeans of Bowden cables, and thus there is a requirement for a novelBowden cable actuating mechanism that can accommodate the varying forceto be exerted thereon. An actuating mechanism that achieves this objectwill now be described.

Referring to FIGS. 4 and 5, the mechanism 10 is provided with an outerhousing 15 incorporating recesses 15A for the receipt of the sheaths 9of the Bowden cables 9. The aforementioned shaft 10A extends within arecess 16 in the housing 15 and carries a cam element 17 that can beturned by means of the shaft 10A and has at an extremity thereof anchorpoints 18 for receiving terminal portions 19 provided at the ends of theBowden cables 9.

FIG. 4 shows the position of the cam element 17 when the arrangement isin the position of adjustment shown in FIG. 2, and a shoulder 17A of thecam element is in abutment with an end stop provided by a web portion 20of the housing 15.

In order to adjust the system from the positon of FIG. 2 towards theposition of FIG. 3, the shaft 10A is turned in an anticlockwisedirection as viewed in FIG. 4. Initially, the end of the Bowden cable 9tensioned by the cam element 17 is at a maximum radius from the centralaxis of the shaft 10A, and thus rotation of the shaft produces themaximum effective longitudinal movement of the cable 9 with a relativelylow mechanical advantage. As the shaft 10A turns clockwise, however, itwill be seen that the cable 9 is wound onto the surface 17B of the cam17 so that the radial distance of the cable 9 from the axis of the shaft10A progressively reduces with the anticlockwise movement of the camelement 17 until, in the end position shown in FIG. 5, the radialdistance of the cable 9 from the centre of the shaft 10A is at aminimum, and the mechanical transmission between the shaft 10A and thecable 9 reduces the maximum mechanical advantage to facilitatetensioning of the cable by the manual actuating mechanism.

The components of the actuating mechanism 10 are shown in more detail inthe exploded view of the FIG. 6, wherein there are shown the housing 15,the cam element 17, the shaft 10A, a connecting peg 21, a helical spring22, a clutch housing 23 and an end cover 24.

The housing 15 is shown in more detail in FIG. 7, wherein FIG. 7A showsa view of the housing similar to that of FIGS. 4 and 5, FIG. 7B shows aside view from the direction of the arrow B of FIG. 7, and FIG. 7C showsa side view from the direction of the arrow C of FIG. 7A. As seen fromFIG. 7B, the side wall of the housing 15 has pair of radial slots 25providing access to the internal recess 16, between which slots isdefined the web 20 referred to above. As shown in FIG. 7B and 7C, therecesses 15A for the cable sheaths 8 are connected via slots 26 to theslots 25, thus enabling insertion of the terminal portions 19 of theBowden cables 9 via the slots 26 and 25 into the recess 16 containingthe cam element 17.

The cam element 17 is shown in more detail in FIG. 8, wherein FIG. 8A isa view of the cam element from the direction seen in FIGS. 4 and 5,shown with the peg 21 in place therein, FIG. 8B is a view in thedirection of the arrow B of FIG. 8A and FIG. 8C is a view in thedirection of the arrow C of FIG. 8A.

As seen in FIG. 8A, the cam element 17 has a bore 30, an aperture 31 ofgenerally oval shape extending along an axis parallel to the bore 30,and a further bore 32 also extending on an axis parallel to the bore 30.

The peg 21 has a portion 33 fitting within the aperture 31 and a portion34 that extends axially from the cam element 17 and has an arcuate shapeas shown in FIG. 8A.

The cam element 17 has a pair of radial slots 35 and a pair of axiallyextending slots 36 for receiving the cables 9 attached to terminalportions 19 as the latter are inserted into the bore 32 via which theyare anchored to the cam element 17.

The shaft 10A is shown in FIG. 9, wherein FIG. 9A is an axial plan viewof the shaft and FIG. 9B is an end view of the shaft taken in thedirection of the arrow B of FIG. 9.

The shaft 10A has a squared end 37 for receiving the actuating leverreferred to above, a main cylindrical portion 38, a further cylindricalportion 39 of reduced diameter, to fit the bore 30 of the cam element17, and a stub portion 40 of further reduced diameter, for engagementwithin a bore 41 (FIG. 7A) of the housing 15. The cylindrical portion 38carries a stepped shoulder 42 of part circular configuration as can beseen from FIG. 9B. The shoulder 42 serves the dual purpose of embracingthe axially extending portion 34 of the peg 21 by which movement istransmitted to the cam element 17, and supporting the helical spring 22that is received in the clutch housing 23. The shoulder portion 42, thespring 22 and the clutch housing 23 cooperate to form a friction clutchretaining the cam element 17 in any set position, as will be describedbelow.

As shown in FIG. 10, the helical spring 22 has inturned ends 22A thatengage within the arcuate recess defined by shoulder 42, the springfitting loosely around the reduced diameter portion of the shoulder 42and being retained axially by the portion of greater diameter.

The clutch housing 23 is shown in transverse section in FIG. 11, whereinthe part 23A comprises a base plate for assembly to the housing 15, thepart 23B comprises a cylindrical shell for receiving the helical spring22 as a friction fit therein, and the part 23C comprises a reduceddiameter bush for receiving and supporting the cylindrical portion 38 ofthe shaft 10A.

With the actuating mechanism in the assembled condition, the spring 22is a tight friction fit within the clutch housing 23, and the portion 34of the peg 21 extends axially with a certain degree of lost motionwithin the arcuate recess of the shoulder 42 and between the ends 22A ofthe spring 22. Thus, with the spring 22 tightly engaged within theclutch housing 23, the two ends 22A of the spring form end stopslimiting the movement of the peg 21 and thus the cam element 17. When itis desired to move the cam element 17 to another position, the shaft 10Ais turned by means of the lever referred to above, and one of the twoends 22A of the spring 22 is thus engaged by a corresponding radial edgeof the shoulder 42. The spring 22 thus becomes wound up upon itself,whereby its diameter is reduced sufficiently to enable it to be rotatedwithin the clutch housing 22, that end 22A of the spring that is engagedbetween the shoulder 42 and the peg 21 serving to transmit rotarymovement to the peg 21 and thus to the cam element 17. Upon release ofthe lever attached to the shaft 10A the spring 22 is allowed to relaxand expand into tight frictional engagement with the clutch housing 23,thereby retaining the cam element 17 in its new position.

Thus it will be seen that the actuating mechanism 10, combines thefunctions of a simple and effective friction clutch and Bowden cableactuating mechanism the mechanical advantage of which is varied tocompensate for changing forces occurring during adjustment of the lumbarsupport provided by the arrangement of FIGS. 1-3.

I claim:
 1. A seat suspension arrangement comprising:a seat frame (5)having a front and a rear and a platform element suspended in the seatframe to provide support for upholstery of the seat, said platformelement comprising a pair of spaced side rails (1) between which extenda plurality of transverse supporting wires (3), said supporting wires(3) incorporating angled portions (3A) which enable the platform elementto extend resiliently relative to said seat frame and to provideresilient support for the upholstery; said side rails (1) each beingcoupled to the seat frame by links (6) which are spaced apart along saidside rails (1); characterized in that the links couple the side rails tothe rear of the seat frame and in that a portion of each of said siderails (1) is further coupled to the front of said seat frame (5) at apoint between adjacent links (6) by adjustable links (9) extendingbetween the seat frame and the side rails a mechanism (10) is coupled tothe adjustable links for adjusting an effective length of the adjustablelinks between the seat frame and the side rails such that when saidadjustable links (9) are in non-contracted conditions, the portions ofthe side rails (1) coupled thereto are proximate the rear of the frameand are rearwardly spaced from the front of the seat frame (5), andwhereby upon contraction of the length of said adjustable links (9), theside portions of said side rails (1) are drawn by the adjustable linksfrom proximate the rear of the frame towards the front of the frame inorder to vary a contour of the platform element.
 2. A seat suspensionarrangement as claimed in claim 1, wherein said seat frame (5) comprisesa backrest portion, said platform element being supported from oppositesides of the backrest portion of the frame (5) by said links (6) andsaid adjustable links (9) being provided in a region of the platformelement for providing a lumbar support, whereby said variation in thecontour of the platform element is such as to adjust the lumbar support.3. A seat suspension arrangement as claimed in claim 1 or 2, wherein theadjustable links comprise Bowden cables (9) extending between the seatframe (5) and said side rails (1) and said mechanism for adjusting theeffective length of the adjustable links (9) comprises an actuatingmechanism (10) for manipulating the Bowden cables (9).
 4. A seatsuspension arrangement as claimed in claim 3 wherein each Bowden cable(9) is coupled to a side rail (1) by means of a bracket (7) linked tothe side rail (1) the bracket providing a ferrule for an outer sheath(8) of the Bowden cable.